Gyro having modulated frequency driven laser

Abstract

A gyro and an operating method is capable of reducing coupling losses which arise when laser beams enter a photodetector and noise which develops due to light entering into a laser from external reflection points. The gyro includes a ring resonator type laser in which laser beams circularly counter propagate, and detects a change in a current or an impedance based on a beat which is generated by the interference of the laser beams counter propagating each other within the laser.

What is claimed is:  
     
       1. A gyro, comprising: 
       a ring resonator type laser in which laser beams circularly counter-propagate each other;  
       a driving source driving said laser with a constant-voltage source, wherein said driving source has been modulated with a frequency which lies outside a frequency band of a beat signal; and  
       beat signal detecting means for detecting the beat signal as a change in a current that flows through said ring resonator type laser.  
     
     
       2. A gyro as defined in  claim 1 , wherein said ring resonator type laser is a semiconductor laser. 
     
     
       3. A gyro as defined in either of claims  1  and  2 , wherein said constant-voltage source is a battery. 
     
     
       4. A gyro as defined in either of claims  1  and  2 , wherein the current change is a change in a frequency of the current. 
     
     
       5. A gyro as defined in either of claims  1  and  2 , wherein the current change is detected as a change in a voltage across a resistor which is connected in series with said ring resonator type laser. 
     
     
       6. A gyro according to  claim 1 , wherein said driving source includes application of a voltage for the modulation to said constant voltage source. 
     
     
       7. A gyro, comprising: 
       a ring resonator type semiconductor laser in which laser beams circularly counter-propagate each other;  
       a driving source driving said ring resonator type semiconductor laser, wherein said driving source has been modulated with a frequency which lies outside a frequency band of a beat signal; and  
       beat signal detecting means for detecting the beat signal as a change in impedance of said semiconductor laser.  
     
     
       8. A gyro as defined in  claim 7 , wherein said ring resonator type semiconductor laser employs a constant-voltage source as its drive source. 
     
     
       9. A gyro as defined in  claim 7 , wherein said ring resonator type semiconductor laser includes a battery as its driving power source. 
     
     
       10. A gyro as defined in  claim 7 , wherein said change in impedance is a change of frequency in impedance.